It is known to attenuate the vibration of a rotorcraft by means of active or passive attenuator devices; passive devices are resonators tuned to a determined frequency, while active devices rely on an actuator that is controlled so as to deliver forces that oppose measured vibration.
French patent No. 2 775 042 and U.S. Pat. No. 6 286 782 describe a passive attenuator system using a helicopter battery as its vibrating weight, the system being tuned to a frequency close to 5 hertz (Hz); in the device described in those patents, the battery is secured to four plane springs forming a tube in which the battery is received; the battery can thus oscillate in a vertical direction and in a lateral direction, at a resonant frequency that depends on the geometry of the plane springs and on the stiffness of the material from which they are made.
Although it presents certain advantages, that system does not enable the resonant frequency to be adjusted to a desired value; unfortunately, the vibration to which the various zones of a rotorcraft are subjected can present components of varying frequency; such variations may be due to varying flight conditions; furthermore, two rotorcraft of the same model may present two different vibration spectra, e.g. because they are fitted out differently.